Muscular dystrophies afflict approximately 1 in 5000 individuals worldwide. The development of animal models to study these diseases is essential in understanding the mechanisms of pathogenesis and to test potential therapies for people afflicted with these diseases. Animal models for some muscular dystrophies, such as facioscapulohumeral muscular dystrophy (“FSHD”) and oculopharyngeal muscular dystrophy (“OPMD”), are still unavailable. Furthermore, some murine models of some muscular dystrophies, whether naturally occurring or genetically engineered, are limited because they do not replicate all the features of the human disease.
An animal model that carries human muscles from individuals with these diseases would serve as a more accurate model, reproducing most, if not all, of the morphological, physiological and genomic features of the muscular dystrophies in man. The present invention describes methods to develop such a model, while solving the problem of the presence of murine myonuclei in the graft. Here, intermittent neuromuscular electrical stimulation (iNMES) is applied to immunodeficient mice engrafted with an immortalized clonal cell line of human myogenic precursor cells (“hMPCs”) that express luciferase (“LHCN” cells).
Previous studies of grafts of hMPCs create hybrid fibers, containing myonuclei of both human and murine origin form, and the fibers express proteins found both in man and in mice. In the present invention, muscle of the host mouse was eliminated by injection of a myotoxin and the myogenic potential of any remaining tissue was suppressed by X-irradiation. Human myogenic precursor cells were then injected. The survival and differentiation of the human muscle tissue were promoted with electrical stimulation. Many of the myofibers in that graft were similar to nearby murine myofibers in size, and they were both innervated by motor neurons and fully differentiated. More importantly, they were comprised almost exclusively of human myonuclei, with minimal contamination by murine myonuclei.